1. Field of the Invention
The present invention relates to a variable capacity refrigerant compressor used for compressing a refrigerant gas in a refrigerating system. More specifically, the present invention relates to a single headed piston type compressor incorporating therein a simple capacity control valve and an improved internal structure for reducing vibratory noise caused by the suction of a refrigerant gas from an external refrigerating system.
2. Description of the Related Art
In variable capacity single-action refrigerant compressors such as variable capacity swash-plate and wobble-plate type compressors used in automobile climate control systems, a rotatable swash plate element or a non-rotatable wobble plate element is supported around a rotating drive shaft as an actuator for actuating reciprocatory motion of single-headed pistons compressing a refrigerant gas within the corresponding cylinder bores. The swash or wobble plate element is held to be turnable about a fulcrum so as to change an angle of inclination thereof with respect to a plane perpendicular to an axis of rotation of the drive shaft. The swash plate or wobble plate element converts the rotation of the drive shaft to a reciprocating movement of respective single headed pistons within the cylinder bores of a cylinder block of the compressor. The swash or wobble plate element is housed in a crank chamber defined by a front chamber arranged in front of the cylinder block, and the angle of inclination of the swash or the wobble plate element is adjustably changed in response to a change in a pressure level prevailing in the crank chamber and acting on respective backs of the single headed pistons which have front acting ends thereof subjecting to a pressure of the refrigerant gas, i.e., a suction pressure when the gas is sucked into the compressor. Since the extent of reciprocation of the single headed pistons, i.e., the stroke of the respective pistons changes so that the back pressure acting on the backs of the pistons and the suction pressure acting on the front acting ends thereof are balanced with one another. Thus, the swash plate or wobble plate element changes its angle of inclination so as to permit the respective pistons to reciprocate at the changed stroke thereof. The pressure prevailing in the crank chamber is controlled by a capacity control valve which is arranged and operates so as to introduce a high pressure discharge gas into the crank chamber in response to a change in the suction pressure.
Nevertheless, the conventional variable capacity single headed piston-type compressor having the capacity control valve must be constructed in such a manner that the crank chamber is always hermetically sealed so as to permit precise control of the pressure prevailing in the crank chamber. Further, the crank chamber is subjected to a high pressure and a high temperature condition provided by a blow-by gas leaking from the respective cylinder bores into the crank chamber during the operation of the compressor. Specifically, when the compressor operates at a full capacity operation under a large refrigerating load, the crank chamber must be subjected to the maximum pressure and very high temperature conditions. Therefore, a shaft sealing device such as a lip seal disposed around the drive shaft of the compressor easily and quickly loses its sealing performance, and moreover, various movable internal elements of compressors such as the pistons, the swash or wobble plate element, and shoes arranged between the swash or wobble plate element and the respective pistons are abraded to result in a reduction in the operation life of the compressor. In this connection, sometimes, either a high quality hard metallic material is selected to produce a swash or wobble plate element or a particular surface treatment for preventing abrasion is applied to the surface of the swash or wobble plate element. Nevertheless, the selection of the metallic material and the application of the particular surface treatment must result in an increase in the production cost of the swash or wobble plate element.
Further, the variable capacity type refrigerant compressor usually has a large pulsation in the suction pressure of the refrigerant gas during the small capacity compressing operation of the compressor, and accordingly, a pulsative noise is caused in an evaporator disposed in a refrigerating system in which the compressor is incorporated. Thus, there is a case in which a variable capacity refrigerant compressor is provided therein with a muffling means for deadening the pulsation in the suction pressure of the refrigerant gas. The provision of the muffling means becomes a cause of an increase in the manufacturing cost of the compressor. Furthermore, the afore-mentioned capacity control valve supplying a discharge pressure gas into the crank chamber of the compressor in response to a change in the suction pressure of the refrigerant gas has a complicated internal structure therein, and must be assembled in the body of the compressor so as to adequately cooperate with fluid passageways arranged in the body of the compressor in order to detect the suction pressure and the pressure prevailing in the crank chamber and a fluid supply passageway running from the discharge chamber to the crank chamber. Therefore, an increase in the manufacturing cost is caused by the provision and assembly of the capacity control valve and by complexity in the formation of the fluid passageways in the body of the compressor.